This invention relates to medical and surgical devices, namely syringes and hypodermic needles in which a medication is injected into a patient or by means of which blood or another fluid is withdrawn from a patient, and is more particularly concerned with a safety syringe in which the needle is shielded to protect patients and medical practitioners against accidental needle-stick injuries. The safety syringe is intended to protect the user from accidental puncture from the needle by means of a needle guard that shields the needle at all times other than during an injection procedure.
It is well appreciated that hypodermic needles present a danger of cross contamination, that is, spreading of pathogens that may be in a patient""s body fluids, to other persons who may have to handle a syringe. Accidental sticking of the needle into a doctor or nurse is a common risk, and steps have been taken to reduce this risk by covering or shielding the needle between injection cycles and after injection cycles. The prior proposals have been far from foolproof, and many of these leave the needle exposed between injections, or may require the practitioner to use both hands to use the syringe, which makes the shield or cover inconvenient to use.
There remains a need for a safety syringe that avoids manual operation, that is, for a syringe in which the practitioner does not need to take any additional steps during an injection cycle, and in which the shield will remain over the needle except when the needle is inserted into a vial for filling the syringe and when the needle is actually being inserted into the patient to inject the medication. By the same token, there remains a need for an effective safety syringe that permits normal, one-hand operation without compromise of safety.
The safety syringe should also permit some limited number of injection cycles, in excess of a single cycle, so that it is possible to fill the syringe from a vial, and then inject the medication into the patient at one, two, or some other number locations. For example, it is sometimes necessary to apply a medicament or local anaesthetic to a patient on both sides of a wound, and the syringe should permit this. It is then desirable for the syringe to lock, with the shield covering the sharp needle, after the last of the injection cycles.
Accordingly, it is an object of the present invention to provide a safety syringe in which the needle is covered before, between, and after the injection cycles, and which avoids the drawbacks of the prior art.
It is another object to provide a safety syringe that is of a straightforward, simple design, and which does not require any special actions on the part of the practitioner.
It is a more specific object to provide a safety syringe with a spring-loaded shield that remains in the cover or guard position except during an injection cycle, which permits one-hand operation, and which locks in the cover or guard position after a predetermined Nth injection cycle.
It is another object to provide a safety syringe with the features of automatic limited cycle, one-hand operation, continuously guarded needle, and programmability (e.g., by manufacturer) for specific operation.
In accordance with one aspect of the present invention, a safety syringe is made with a a tubular barrel that has a proximal end and a distal end; a hollow needle affixed to the distal end of the barrel and extending distally from the barrel; and a protective shield that covers the needle and is movable proximally-distally so that the shield has a distal or extended protective position and a proximal exposed position. The protective shield has a tubular slide member that fits slidably over the distal end of the barrel and a needle cover that projects distally from the slide member out to cover the needle. A spring or other biasing device urges the slide member distally so that the protective shield goes its distally extended protective position. In that position, the needle cover extends distally beyond a tip of said needle so that the patient and practitioner are protected from the sharp end of the needle.
A series of gated tracks are provided on the barrel and a track follower that rides in the gated tracks is situated on a facing surface of the slide member. The track follower, which can be a radially oriented pin, projects into one of the tracks so it can follow the tracks, and pass through gates successively along the series of tracks. Alternatively, the tracks can be formed on the slide of said protective shield, with the pin or follower on the barrel of the syringe.
The gated tracks are arranged such that the protective shield is initially disposed in its protective position. The follower travels in the tracks, back and forth, in sequence to permit the shield to retract proximally to the exposed position, and then back to the covered or protective position. The follower travels from one track to another in turn to permit the shield to extend to the protective position after a first injection cycle; then in a successive one of the tracks to permit the shield to retract to the exposed position for at least one further injection cycle; and then the follower travels to reach a lock position at a final injection cycle.
In some of many possible preferred embodiments the series of tracks includes three tracks, and said track follower reaches a lock position in the third tracks at the end of a second injection cycle. Alternatively, there can be at least four tracks, so that the track follower reaches the lock position at the end of a predetermined injection cycle beyond a second injection cycle, i.e., after three or after four injection cycles. In other alternative embodiments, one track in the series of tracks provides a selective lock position in which the shield is held in a proximal position in which the needle is at least partly exposed.
The tracks or channels can be of programmed lengths to accommodate the need to limit the depth of injection. With a given track shortened or lengthened the needle can be limited to a shallower injection depth or permitted to go to a deeper injection depth, as required for a given application.
Favorably, the gates included in the gated tracks are in the form of uni-directional flaps with a hinge axis that is directed radially, in respect to the barrel of the syringe.
An alternative embodiment the series of gated tracks or channels can be on a sleeve that rotates around the circumference of the barrel of the syringe, controlling the shield extension and retraction with cam action.
An important aspect of this invention lies in the use of one-way gates, redirection gates, and programmed channel lengths to create a logical sequence to control the action of the shield. The arrangement of the tracks or channels can be manifested in many forms.
The safety needle of this invention is fully automatic, with the shield sliding out of the way upon injection and sliding back over the needle when the injection is complete. The safety syringe arrangement of this invention automatically limits the number of injections for which the syringe can be used, thus preventing a needle that has been used on one patient from contacting a practitioner or another patient. The incorporation of mechanical logic allows the practitioner to operate the syringe with one hand, except when the logic sequence requires a manual input, such as to unlock from a lock position.
The automatic, limited cycle operation is achieved through a variety of mechanical logic mechanism that are built into the syringe at the time of manufacture. A basic-cycle logic sequence, or standard sequence, would be inject vialxe2x80x94inject patientxe2x80x94lock. However, the syringes can be produced with other logic sequences by altering the mechanical logic at the time of manufacture. One alternative logic sequence could be inject vialxe2x80x94inject patientxe2x80x94hold openxe2x80x94manual releasexe2x80x94lock.
The above and many other objects, features, and advantages of this invention will be more fully appreciated from the ensuing description of a few selected preferred embodiments, which is to be read in conjunction with the accompanying Drawing.